Quantal Analysis of Minimal Postsynaptic Potentials in Hippocampal Slices: Binomial Model

Abstract

It has been already noted in Chapter 12 that recording of UPSPs is preferable for a more precise quantal analysis. However, the recording of UPSPs is not practical for studies of long-lasting events in neurones of vertebrate CNS. In fact, simultaneous recordings from two hippocampal neurones in our in vivo experiments [90] revealed UPSPs in only few cases (Sect. 12.3). Even under more stable conditions of recordings from hippocampal slices, the success rate of UPSPs from CA3-CA1 pairs was found to be very low [351, 864, 865]. In addition, several other problems are not resolved for CNS neurones (Chaps. 7, 11). I mention here the high S„ and also small sample sizes (N) because of time limitations of intracellular recordings from healthy cells and necessity of “stationarity” for reliable statistical analysis. The limitation of N might be illustrated by our in vivo studies (Chaps. 11 and 12), as well as by studies of other authors. An example is the publication on unitary IPSPs in the Mauthner cell [528] with the average number of counts equal to 161 and with <70 counts in some cases. All these problems, common to most neurones of the CNS, are heavily aggravated for recordings from higher levels of the mammalian brain (e.g. cortical structures) and especially for in vivo recordings. Therefore, we decided to expand and reinforce the previous quantal analysis by additional experiments on the CAI area of hippocampal slices. Initial attempts to apply the quantal hypothesis to recordings from hippocampal slices were reviewed in Sections 7.8.5 and 7.9.4 (see also our initial data in Sect. 11.5). Before we started the present experiments, only preliminary data on statistical analysis of EPSPs recorded in region CA1 [33] were published. The related full publications appeared recently [351, 864, 865].